基于外差双光学频率梳的绝对距离超精密测量方法研究

With the development of large scale sophisticated scientific experimental device and ultra-precision equipment manufacturing technology, laser absolute distance measurement technology has been widely used. However, the current methods can not achieve nm level ultra-precision distance measurement. Besides, high measurement accuracy and efficiency can not realize at the same time. Aiming these problems, a multi-wavelength absolute distance interferometry based on heterodyne dual optical frequency combs is proposed in this project. The highest accuracy distance measurement is achieved by single comb mode. The measureable range is extended by orders of synthetic wavelengths. The transfer channel of interference ranging information for multi-comb modes will be revealed. The many different scale synthetic wavelengths will be generated synchronously. The coarse and fine distance measurement can thus realize at the same time. In this way, high accuracy and high efficiency absolute distance measurement can be achieved. To keep the phase detection error from nm level measurement accuracy, a PDH theory based frequency stabilization method for frequency comb is proposed to avoid the phase error from extra modulation needed in current methods. Meanwhile, the phase detection error from noise spectrum will be suppressed based on the multi-channel phase-locking detection. Moreover, the distance measurement information can be merged to reduce the affect from phase detection error. This project will accelerate the development of absolute distance measurement technology with Chinese independent intellectual property rights. It will has a important role in enhancing the level of large scale sophisticated scientific experimental device and ultra-precision equipment manufacturing technology in our country.

随着大型尖端科学实验装置与大型超精密装备制造技术的不断进步，激光绝对距离测量技术得到广泛应用。但现有激光测距技术普遍存在难以实现nm量级超精密测量、难以兼顾测量精度与效率的问题。针对这些问题，本项目探索一种基于外差双光学频率梳的多波长干涉测距方法，利用单个频率梳齿进行最高精度的距离测量，由各级合成波长进行测程扩展，深入剖析多梳齿干涉测距信息的转移途径，研究多个不同尺度合成波长的同步生成理论，同时进行距离粗测与精测以兼顾测量精度与效率。为防止相位测量误差制约nm量级测距精度的实现，提出基于PDH原理的频率梳稳频方法以避免附加调制引入的相位测量误差，研究基于多通道锁相探测理论以抑制噪声频谱带来的相位测量误差，并通过多个梳齿的测距信息融合进一步抑制相位测量误差对测距精度的作用效果。本项目将促进具有自主知识产权的激光测距技术发展，对提升我国大型尖端实验装置与超精密装备制造技术的水平有重要推动作用。

以大型飞机装配为代表的高端制造业和以大型对撞机为代表的前沿科学实验装置对激光测距技术需求迫切。光学频率梳的出现促进了该技术的发展，但现有基于光频梳的激光测距方法仍存在难以兼顾测量范围、精度与效率的问题，无法完全满足上述领域的要求。本课题旨在提出一种可以兼顾大范围、快速和高精度特性的多波长激光干涉测量方法，本课题主要研究内容如下：. (1)提出了一种基于外差双光频梳的多波长干涉测距方法，该方法以外差双光频梳作为光源，利用其中的众多梳齿同步生成了多个不同尺度的粗测和精测合成波长，对光频梳中多梳齿的干涉测距信息进行了融合处理。分析及实验结果表明，该方法可实现大范围、快速、高精度距离测量，可将测相误差引入的距离测量不确定度从21.3μm减小为8μm。. (2)提出了一种基于PDH原理的腔内调相频率梳稳定控制方法，通过探测谐振腔反射光中包含的梳齿间干涉信号，利用相位调制信号对其解调得到反馈控制误差信号，对该方法中误差信号的生成机理进行了完整建模。仿真及实验结果表明，利用上述稳定控制方法可以持续稳定的生成梳齿数量达到33条，光谱范围达到294.4GHz的光频梳。. (3)提出了一种基于数字锁相放大的多梳齿测距相位分离与提取方法，根据干涉信号频谱特点，利用数字锁相放大探测技术实现了多梳齿测距相位信息的分离与提取。仿真结果表明，利用上述多梳齿测距相位分离与提取方法对中心15条梳齿的相位测量误差小于±0.01°。. 最后，对基于外差双光频梳的多波长干涉测距系统进行了实验验证。实验结果表明，其30min内的测量相对稳定性可达到4.1×10-7，20m距离处的测量相对不确定度达到5.3×10-7。. 在项目资助下，累计发表SCI论文3篇，EI论文2篇，1篇论文获得ISMTII2017国际会议最佳论文奖，获授权中国发明专利1项，申请中国发明专利6项，培养硕士研究生5名，指导本科毕业设计6名。